The compounds of formula II, below, are useful intermediates in the preparation of certain quinolone antibacterial agents. For example, BOC -or acetyl-protected (2S,4S)-4-amino-2-methylpyrrolidine (II, in which R.sup.2 is -BOC or acetyl) are intermediates in the synthesis of 7-((2S,4S)-4-amino-2-methyl-1-pyrrolidinyl)-1-(2,4-difluorophenyl)-1,4-dih ydro-6-fluoro-4-oxo-quinolone-3-carboxylic acid, the preparation of which is described in U.S. Pat. No. 4,962,112. ##STR2##
Reported syntheses of compounds II are limited in their ability to provide stereochemically pure products with a minimum of reaction steps, and in the availability of the necessary starting materials. Thus there is a continuing need to develop more effective syntheses of II. The compounds and process of the present invention enable the production of compound II from starting materials which are readily available and/or with yields which were previously unattainable.